Full-Field Deformation Measurement of 2D-DIC Based on Virtual Camera Array in Small Field of View

In a small field of view, 2-D digital image correlation (2D-DIC) is limited by the size of the field of view, making it difficult to achieve large-scale deformation measurement with one camera. At the same time, it cannot be guaranteed that the camera’s optical axis is always perfectly perpendicular to the measurement surface, and the resulting out-of-plane displacement will lead to significant measurement errors in 2D-DIC. Therefore, this article proposes a 2D-DIC full-field deformation measurement method based on virtual camera array in small field of view. A virtual camera array composed of one camera is used to capture images in small field of view. An image stitching method based on subset correlation and frequency-domain shift theorem and a speckle fusion method based on sine trigonometric function are proposed, which achieves high-precision image stitching and obtains high-resolution images of samples. Dual-reflector technology combined with static error compensation is used to improve the measurement accuracy of the fields. The experimental results show that the maximum and minimum absolute errors of axial strain are 34.6089 and
$2.3237 \, \mu \varepsilon $
, respectively, and the average relative error is 5.4300%.